Speaks poorly for the state of laws in America.
In a perfect state of law, individuals do not have to think of their personal security and guns are not needed.

Bisaal,

The problem is not the laws in this country-- murder, on whatever scale, is unlawful, and has been so for a long time.

The problem is the people, the same noble, base, peaceful, violent people you will find anywhere else on the planet.

Or, as French say (as it works out in English): "If murder is to be abolished, would the assassins be so kind as to begin?"

Hale Adams
Pikesville, People's Democratic Republic of Maryland

A question: in America, can a bystander shoot and kill a person that is engaged in beating or killing another person?
That is, self-defense is of course allowed but can a bystander engage in maintaining public peace?

Bisaal: Yes. Under California law if you honestly and reasonably believe that another person is about to suffer serious bodily harm or death you are entitled to use only enough force necessary to counter the attack. You can look at Judicial Council of California Criminal Jury Instruction 505 for the specifics.